This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-292938, filed Sep. 26, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a defect detection apparatus which irradiates inspection objects such as a semiconductor wafer with an illuminating light and performs defect inspection based on an image of the light from the inspection object, and a storage medium readable by a computer, in which a program is stored.
2. Description of the Related Art
For example, in a semiconductor manufacturing process, macro inspection of damage, dust, surface irregularity, dirt, and the like in a semiconductor wafer surface is performed. This macro inspection comprises: irradiating the semiconductor wafer surface with an illuminating light; picking up images of regular reflected light, diffracted light, and scattered light by an image pickup apparatus; and image-processing the image data to detect defects such as damage, dust, surface irregularity, and dirt in the semiconductor wafer surface.
FIG. 3 is a schematic diagram of a macro inspection apparatus according to related art. A semiconductor wafer 2 is laid on a stage 1, an illuminating unit 3 is disposed obliquely above the wafer, and an image pickup unit 4 is disposed in an opposite position with respect to the illuminating unit 3 with respect to the semiconductor wafer 2. In the macro inspection apparatus, when the semiconductor wafer 2 is irradiated with the illuminating light from the illuminating unit 3, and the image of a diffracted light from the semiconductor wafer 2 is picked up by the image pickup unit 4, an illuminating angle is variably set with respect to the semiconductor wafer 2 in order to detect the diffracted light.
In the setting method of the illuminating angle, while the semiconductor wafer 2 is irradiated with the illuminating light from the illuminating unit 3, the illuminating angle, that is, the inclination angle of the illuminating unit 3 with respect to the semiconductor wafer 2 is varied, for example, in a range of +20xc2x0 to xe2x88x9220xc2x0. Subsequently, the image of the diffracted light from the semiconductor wafer 2 is picked up by the image pickup unit 4, the angle at which primary diffracted light can be taken in is obtained from the image data, and the illuminating unit 3 is set to the angle.
However, the semiconductor wafers 2 to be inspected include a wafer in which the shape and direction of the pattern of a formed chip differ with each type of wafer, and a wafer in which the pitch of the pattern differs. It is assumed that these semiconductor wafers 2 are inspected. Then, every time the type of the semiconductor wafer 2 changes, the illuminating angle is varied, for example, in a range of +20xc2x0 to xe2x88x9220xc2x0. While the picked-up image data is referred to, the angle of incidence for satisfactorily taking in the primary diffracted light has to be obtained to set the inclination angle of the illuminating unit 3, and much time is required for the inspection.
Moreover, because of a difference of the shape, direction, or pitch of the pattern of the chip formed in the semiconductor wafer 2, the angle of incidence and the direction for the image pickup unit to satisfactorily take in the diffracted light from the pattern on the semiconductor wafer 2 differ. Therefore, the illuminating unit 3 cannot necessarily be set to an angle and direction optimum for taking in the diffracted light.
An object of the present invention is to provide a defect detection apparatus in which illuminating light can be set to an optimum angle to take in diffracted light necessary for performing an inspection.
Another object of the present invention is to provide a storage medium readable by a computer, in which a program for setting the illuminating light to the optimum angle to take in the diffracted light necessary for performing the inspection is stored.
According to the present invention, there is provided a defect detection apparatus comprising: an illuminating unit which irradiates an inspection object with an illuminating light; and an image pickup unit which picks up an image of a diffracted light from the inspection object to perform defect inspection of the inspection object from image data picked up by the image pickup unit, the apparatus further comprising: a diffraction angle calculation unit to obtain the diffraction angle of the illuminating light with respect to the inspection object, which is optimum for picking up the image of the diffracted light, based on design information of the inspection object; and an illuminating setting unit which sets the angle of incidence of the illuminating unit to the diffraction angle calculated by the diffraction angle calculation unit.
Advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.